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液晶含量对聚合物/液晶复合膜电光特性的影响--从正型向反型显示模式的转变 总被引:3,自引:2,他引:1
预聚物与正性液晶以适量配比合成的聚合物/液晶复合膜通常呈正型显示,即膜在关态时呈散射态,在开态时呈透射态。然而实验发现,用高的液晶配比合成的膜在适度电压驱动下能呈现反型显示,即这种膜在关态时呈透射态,在适度电压作用下呈散射态。在制膜过程中,如能将液晶做沿面取向处理,则膜的反型效应更加明显。用聚合物/液晶复合膜的反型显示机理,可开发出一系列新的光学显示器件。本实验研究了这种反型模式器件的电光特性,并建立相关的结构模型解释了实验结果。 相似文献
3.
Tuning Local Molecular Orientation–Composition Correlations in Binary Organic Thin Films by Solution Shearing 下载免费PDF全文
Wei Ma Julia Reinspach Yan Zhou Ying Diao Terry McAfee Zhenan Bao Harald Ade 《Advanced functional materials》2015,25(21):3131-3137
A general impact of solution shearing on molecular orientation correlation is observed in polymer:fullerene organic solar cells in which one of the components forms fibrils or aggregates. Further investigation with polarized soft X‐ray scattering reveals that solution shearing induces more face‐to‐face orientation relative to the interface of two components compared to spin‐coating. This impact is shearing speed dependent, that is, slow shearing speed can induce more face‐to‐face orientation than a fast shearing speed. These results demonstrate that solution shearing is an effective method to control the relative molecular orientation. Solution shearing can also modify the domain size and average composition variations. 相似文献
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Rapid and Facile Formation of P3HT Organogels via Spin Coating: Tuning Functional Properties of Organic Electronic Thin Films 下载免费PDF全文
Cameron S. Lee Wen Yin Adam P. Holt Joshua R. Sangoro Alexei P. Sokolov Mark D. Dadmun 《Advanced functional materials》2015,25(36):5848-5857
Poly(3‐hexyl thiophene) (P3HT) is widely regarded as the benchmark polymer when studying the physics of conjugated polymers used in organic electronic devices. P3HT can self‐assemble via π–π stacking of its backbone, leading to an assembly and growth of P3HT fibrils into 3D percolating organogels. These structures are capable of bridging the electrodes, providing multiple pathways for charge transport throughout the active layer. Here, a novel set of conditions is identified and discussed for P3HT organogel network formation via spin coating by monitoring the spin‐coating process from various solvents. The development of organogel formation is detected by in situ static light scattering, which measures both the thinning rate by reflectance and structural development in the film via off‐specular scattering during film formation. Optical microscopy and thermal annealing experiments provide ex situ confirmation of organogel fabrication. The role of solution characteristics, including solvent boiling point, P3HT solubility, and initial P3HT solution concentration on organogel formation, is examined to correlate these parameters to the rate of film formation, organogel‐onset concentration, and overall network size. The correlation of film properties to the fabrication parameters is also analyzed within the context of the hole mobility and density‐of‐states measured by impedance spectroscopy. 相似文献
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Optimization of Solubility,Film Morphology and Photodetector Performance by Molecular Side‐Chain Engineering of Low‐Bandgap Thienothiadiazole‐Based Polymers 下载免费PDF全文
Ji Qi Xiaokang Zhou Dezhi Yang Wenqiang Qiao Dongge Ma Zhi Yuan Wang 《Advanced functional materials》2014,24(48):7605-7612
A series of donor–acceptor (D‐A) type low‐bandgap polymers containing the terthiophene and thieno[3,4‐b]thiadiazole units in the main chain but different numbers of identical side chains are designed and synthesized in order to study the effect of side chain on the polymer properties and optimize the performance of polymer photodetectors. Variation in the side chain content can influence the polymer solubility, molecular packing, and film morphology, which in turn affects the photodetector performance, particularly with regard to the photoresponsivity and dark current. X‐ray diffraction patterns indicate that molecular ordering increases with more side chains. Atomic force microscopy shows that appropriate morphology of the active layer in the polymer photodetector is necessary for high photocurrent and low dark current. Using BCP as a hole blocking layer (10 nm), the photodetector based on P4 exhibits the optimized performance with specific detectivity of 1.4 × 1012 Jones at 800 nm, which is among the best reported values for polymer photodetectors and even comparable to that of a silicon photodetector. 相似文献
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Improved Charge Generation via Ultrafast Effective Hole‐Transfer in All‐Polymer Photovoltaic Blends with Large Highest Occupied Molecular Orbital (HOMO) Energy Offset and Proper Crystal Orientation 下载免费PDF全文
Feng Jin Jianyu Yuan Wenping Guo Yalong Xu Yannan Zhang Chuanxiang Sheng Wanli Ma Haibin Zhao 《Advanced functional materials》2018,28(31)
Improved charge generation via fast and effective hole transfer in all‐polymer solar cells (all‐PSCs) with large highest occupied molecular orbital (HOMO) energy offset (ΔEH) is revealed utilizing ultrafast transient absorption (TA) spectroscopy. Blending the same nonfullerene acceptor poly{[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene) (N2200) with three different donor polymers produces all‐polymer blends with different ΔEH. The selective excitation of N2200 component in blends enables to uncover the hole transfer process from hole polaron‐induced bleaching and absorption signals probed at different wavelength. As the ΔEH is enhanced from 0.14 to 0.37 eV, the hole transfer rate rises more than one order and the hole transfer efficiency increases from 12.9% to 86.8%, in agreement with the trend of internal quantum efficiency in the infrared region where only N2200 has absorption. Additionally, Grazing‐incidence wide‐angle X‐ray scattering measurements indicate that face‐on crystal orientation in both polymer donor and acceptor also plays an important role in facilitating the charge generation via hole transfer in all‐PSCs. Hence, large ΔEH and proper crystal orientation should be considered in material design for efficient hole transfer in N2200‐based heterostructures. These results can provide valuable guidance for fabrication of all‐PSCs to further improve power conversion efficiency. 相似文献
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Peng Liu Sheng Dong Feng Liu Xiaowen Hu Liqian Liu Yaocheng Jin Shengjian Liu Xiong Gong Thomas P. Russell Fei Huang Yong Cao 《Advanced functional materials》2015,25(41):6458-6469
A series of conjugated polymers using naphtho[1,2‐c:5,6‐c]bis[1,2,5]thiadiazole and benzodithiophene alternating backbone is synthesized to investigate the effect of side chain substitution on conjugated donor–acceptor polymer on electronic, morphological, and photovoltaic properties. It is found that light absorption and frontier energy levels of the resultant polymers are strongly affected by the side chains. The thin film morphology, crystal structure, crystallinity, and orientation also depend on the side chains; the side chain type affects more in the π–π stacking direction, while the side chain density plays a significant role in the lamellar packing direction. The thickness of the active layer also influences the performance of the solar cells with some materials showing enhanced performance with thicker active layers. The best solar cell device in this study has power conversion efficiencies of 8.14%, among the highest in materials of similar structure. 相似文献
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Yamamoto T Hasegawa T Sasaki M Hongo H Tabata C Liu Z Li M Amizuka N 《Journal of electron microscopy》2012,61(2):113-121
This study was designed to elucidate details of the structure and formation process of the alternate lamellar pattern known to exist in lamellar bone. For this purpose, we examined basic internal lamellae in femurs of young rats by transmission and scanning electron microscopy, the latter employing two different macerations with NaOH at concentrations of 10 and 24%. Observations after the maceration with 10% NaOH showed that the regular and periodic rotation of collagen fibrils caused an alternation between two types of lamellae: one consisting of transversely and nearly transversely cut fibrils, and the other consisting of longitudinally and nearly longitudinally cut fibrils. This finding confirms the consistency of the twisted plywood model. The maceration method with 24% NaOH removed bone components other than cells, thus allowing for three-dimensional observations of osteoblast morphology. Osteoblasts extended finger-like processes paralleling the inner bone surface, and grouped in such a way that, within a group, the processes arranged in a similar direction. Transmission electron microscopy showed that newly deposited fibrils were arranged alongside these processes. For the formation of the alternating pattern, our findings suggest that: (1) osteoblasts control the collagen fibril arrangement through their finger-like process position; (2) osteoblasts behave similarly within a group; (3) osteoblasts move their processes synchronously and periodically to promote alternating different fibril orientation; and (4) this dynamic sequential deposition of fibrils results in the alternate lamellar (or twisted plywood) pattern. 相似文献
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Two new polyoxetane polymers bearing azobenzene‐type chromophore pendants were prepared, and their photoinduced molecular orientation and relaxation were studied. The two polymers differ in the mode of attachment of the chromophores, which are either laterally ( Pox 1 ) or perpendicularly ( Pox 2 ) bound to the polymer backbone. The two polymers reveal unusually fast (∼2 s to saturation at 0.4 W/cm2) photoinduced reorientation of chromophores and decay behavior at room temperature. Side‐on attachment of the chromophores ( Pox 1 ) results in a significantly faster response to polarized light and higher maximum birefringence than end‐on attachment. The kinetics of photoinduced orientation and relaxation decay were quantitatively analyzed and the results are discussed in relation to the structures of the polymers. 相似文献
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激励态向列微滴散射理论的修正及其参量拟合 总被引:3,自引:2,他引:3
用反常衍射(ADA)理论与实验数据优化拟合方法分析了聚合物分散液晶(PDLC)微滴在633nm激光照射下的散射特性与微滴尺寸、聚合物折射率的关系。在聚合物分散液晶中除了液晶微滴本身的散射以外,还有例如界面散射、杂质散射、材料折射率不均匀等附加散射因子,考虑这些因素以后对反常衍射散射理论进行了修正,提出用参量拟合来测量聚合物分散液晶中聚合物折射率、微滴半径以及液晶体积百分数等参量的方法。测量了微滴的直径在2μm左右聚合物分散液晶的参量。结果表明,对聚合物分散液晶聚合物折射率的误差在5%以内,而对液晶体积分数的测试误差较大,达到10%左右。 相似文献
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Sungwon Lee Gregory A. Becht Byeongdu Lee Christopher T. Burns Millicent A. Firestone 《Advanced functional materials》2010,20(13):2063-2070
The preparation and polymerization of a bifunctional imidazolium‐based ionic liquid (IL) monomer that incorporates both a vinyl group and a thiophene moiety is reported. Potentiodynamic electropolymerization of the monomer produces an optically birefringent polymer film that strongly adheres to the electrode surface. Fourier transform IR spectroscopy shows that polymerization occurs through both the vinyl and thienyl groups. Cylic voltammetry (CV) is used to determine the polymer oxidation potential (1.66 V) and electrochemical bandgap, Eg, of 2.45 eV. The polymer exhibits electrochromism, converting from yellow in the neutral form (λmax = 380 nm) to blue in the polaronic state at 0.6 V (λmax = 672 nm) and to blue‐grey in the bipolaronic state at 1.2 V (λmax > 800 nm). Topographic atomic force microscopy (AFM) images reveal isolated (separated) fibrils. Grazing‐incidence small‐angle X‐ray scattering (GISAXS) studies indicate a lamellar structure with a lattice spacing of 3.2 nm. Wide‐angle X‐ray diffraction (WAXD) studies further suggest that the polymerized thiophene sheets are oriented perpendicular to the polymerized vinylimidazolium. The electrical conductivity, as determined by four‐probe dc conductivity measurements was found to be 0.53 S cm?1 in the neutral form and 2.36 S cm?1 in the iodine‐doped state, values higher than typically observed for polyalkylthiophenes. The structural ordering is believed to contribute to the observed enhancement of the electrical conductivity. 相似文献
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Sergei Pyshkin John Ballato Michael Bass Giorgio Turri 《Journal of Electronic Materials》2008,37(4):388-395
Evolution of luminescence is reported from GaP crystals that were grown over 40 years ago. This is the longest running cycle
of experiments to study the temporal effects of crystal lattice and impurity ordering. The results clearly indicate impurity
ordering and the formation of a new type of crystal lattice in which periodically disposed impurities modify and improve properties
of the crystal. A high-density exciton system bound to a nitrogen impurity superlattice and GaP:N, GaP:N:Sm nanocrystals distributed
in transparent fluorine-containing polymers will be used as the base elements for a new generation of optoelectronic devices. 相似文献
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Directed Self‐Assembly as a Route to Ferromagnetic and Superparamagnetic Nanoparticle Arrays 下载免费PDF全文
Laura T. Schelhas Richard A. Farrell Udayabagya Halim Sarah H. Tolbert 《Advanced functional materials》2014,24(44):6956-6962
Block co‐polymer patterns are attractive candidates for nanoparticle assemblies. Directed self‐assembly of block co‐polymers in particular allows for long range ordering of the patterns, making them interesting scaffolds for the organization of magnetic particles. Here, a method to tune the channel width of polymer‐derived trenches via atomic layer deposition (ALD) of alumina is reported. The alumnia coating provides a much more thermally robust pattern that is stable up to 250 °C. Using these patterns, magnetic coupling in both ferromagnetic and superparamagnetic nanocrystal chains is achieved. 相似文献
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Combinatorial Study of Temperature‐Dependent Nanostructure and Electrical Conduction of Polymer Semiconductors: Even Bimodal Orientation Can Enhance 3D Charge Transport 下载免费PDF全文
Sangsik Park Moo Hyung Lee Kwang Seok Ahn Hyun Ho Choi Jihye Shin Jie Xu Jianguo Mei Kilwon Cho Zhenan Bao Dong Ryeol Lee Moon Sung Kang Do Hwan Kim 《Advanced functional materials》2016,26(26):4627-4634
Temperature‐dependent (80–350 K) charge transport in polymer semiconductor thin films is studied in parallel with in situ X‐ray structural characterization at equivalent temperatures. The study is conducted on a pair of isoindigo‐based polymers containing the same π‐conjugated backbone with different side chains: one with siloxane‐terminated side chains (PII2T‐Si) and the other with branched alkyl‐terminated side chains (PII2T‐Ref). The different chemical moiety in the side chain results in a completely different film morphology. PII2T‐Si films show domains of both edge‐on and face‐on orientations (bimodal orientation) while PII2T‐Ref films show domains of edge‐on orientation (unimodal orientation). Electrical transport properties of this pair of polymers are also distinctive, especially at high temperatures (>230 K). Smaller activation energy (E A) and larger pre‐exponential factor (μ 0) in the mobility‐temperature Arrhenius relation are obtained for PII2T‐Si films when compared to those for PII2T‐Ref films. The results indicate that the more effective transport pathway is formed for PII2T‐Si films than for the other, despite the bimodally oriented film structure. The closer π–π packing distance, the longer coherence length of the molecular ordering, and the smaller disorder of the transport energy states for PII2T‐Si films altogether support the conduction to occur more effectively through a system with both edge‐on and face on orientations of the conjugated molecules. Reminding the 3D nature of conduction in polymer semiconductor, our results suggest that the engineering rules for advanced polymer semiconductors should not simply focus on obtaining films with conjugated backbone in edge‐on orientation only. Instead, the engineering should also encounter the contribution of the inevitable off‐directional transport process to attain effective transport from polymer thin films. 相似文献
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Unraveling the Main Chain and Side Chain Effects on Thin Film Morphology and Charge Transport in Quinoidal Conjugated Polymers 下载免费PDF全文
Xuncheng Liu Bo He Andrés Garzón‐Ruiz Amparo Navarro Teresa L. Chen Matthew A. Kolaczkowski Shizhen Feng Lianjie Zhang Christopher A. Anderson Junwu Chen Yi Liu 《Advanced functional materials》2018,28(31)
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A Versatile Method to Fabricate Highly In‐Plane Aligned Conducting Polymer Films with Anisotropic Charge Transport and Thermoelectric Properties: The Key Role of Alkyl Side Chain Layers on the Doping Mechanism 下载免费PDF全文
Amer Hamidi‐Sakr Laure Biniek Jean‐Louis Bantignies David Maurin Laurent Herrmann Nicolas Leclerc Patrick Lévêque Vishnu Vijayakumar Nicolas Zimmermann Martin Brinkmann 《Advanced functional materials》2017,27(25)
A general method is proposed to produce oriented and highly crystalline conducting polymer layers. It combines the controlled orientation/crystallization of polymer films by high‐temperature rubbing with a soft‐doping method based on spin‐coating a solution of dopants in an orthogonal solvent. Doping rubbed films of regioregular poly(3‐alkylthiophene)s and poly(2,5‐bis(3‐dodecylthiophen‐2‐yl)thieno[3,2‐b ]thiophene) with 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ) yields highly oriented conducting polymer films that display polarized UV–visible–near‐infrared (NIR) absorption, anisotropy in charge transport, and thermoelectric properties. Transmission electron microscopy and polarized UV–vis–NIR spectroscopy help understand and clarify the structure of the films and the doping mechanism. F4TCNQ? anions are incorporated into the layers of side chains and orient with their long molecular axis perpendicular to the polymer chains. The ordering of dopant molecules depends closely on the length and packing of the alkyl side chains. Increasing the dopant concentration results in a continuous variation of unit cell parameters of the doped phase. The high orientation results in anisotropic charge conductivity (σ) and thermoelectric properties that are both enhanced in the direction of the polymer chains (σ = 22 ± 5 S cm?1 and S = 60 ± 2 µV K?1). The method of fabrication of such highly oriented conducting polymer films is versatile and is applicable to a large palette of semiconducting polymers. 相似文献
17.
Yeon‐Ju Kim Nam‐Koo Kim Won‐Tae Park Chuan Liu Yong‐Young Noh Dong‐Yu Kim 《Advanced functional materials》2019,29(23)
Ordering of semiconducting polymers in thin films from the nano to microscale is strongly correlated with charge transport properties as well as organic field‐effect transistor performance. This paper reports a method to control nano to microscale ordering of poly{[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)} (P(NDI2OD‐T2)) thin films by precisely regulating the solidification rate from the metastable state just before crystallization. The proposed simple but effective approach, kinetically controlled crystallization, achieves optimized P(NDI2OD‐T2) films with large polymer domains, long range ordered fibrillar structures, and molecular orientation preferable for electron transport leading to dramatic morphological changes in both polymer domain sizes at the micrometer scale and molecular packing structures at nanoscales. Structural changes significantly increase electron mobilities up to 3.43 ± 0.39 cm2 V?1 s?1 with high reliability, almost two orders of enhancement compared with devices from naturally dried films. Small contact resistance is also obtained for electron injection (0.13 MΩ cm), low activation energy (62.51 meV), and narrow density of states distribution for electron transport in optimized thin films. It is believed that this study offers important insight into the crystallization of conjugated polymers that can be broadly applied to optimize the morphology of semiconducting polymer films for solution processed organic electronic devices. 相似文献
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Nanoporous Silver Thin Films: Multifunctional Platforms for Influencing Chain Morphology and Optical Properties of Conjugated Polymers 下载免费PDF全文
Disordered nanoporous silver (NPAg) thin films fabricated by a thermally assisted dewetting method are employed as a platform to influence chain alignment, morphology, and optical properties of three well‐known conjugated polymers. Grazing‐incidence wide‐angle X‐ray scattering (GIWAXS) measurements show that the porous structure of the metal induces close π–π stacking of poly(3‐hexylthiophene) (P3HT) chains and extended, planar chain conformations of poly(9,9‐di‐n‐octylfluorenyl‐2,7‐diyl) (PFO) and poly[(9,9‐di‐n‐octylfluorenyl‐2,7‐diyl)‐alt‐(benzo[2,1,3]thiadiazol‐4,8‐diyl)] (F8BT). A greater degree of vertically‐oriented P3HT chains are found on NPAg compared with planar Ag. However, PFO and F8BT chain alignment is only affected when pore size is large. The optical properties of NPAg films are investigated by transmission and back‐scattering spectroscopies. Strong back‐scattering is observed for all NPAg morphologies, especially for NPAg with small pore sizes. Photoluminescence spectroscopy of conjugated polymer layers on NPAg showed pronounced emission enhancements (up to factors of 26) relative to layers on glass. The enhancements are attributed primarily to: 1) redistribution of conjugated polymer emission by Ag; 2) redirection of emission by polymer‐filled nanopores; and 3) local electromagnetic field effects. This work demonstrates the potential of NPAg‐thin films to influence molecular chain morphology and to improve light‐extraction in organic optoelectronic devices. 相似文献
19.
Zhongxiang Peng Yaowen Zhang Xiaokang Sun Wenchao Zhao Fenggang Bian Yanhou Geng Long Ye Chunming Yang 《Advanced functional materials》2023,33(14):2213248
Characterizing the bulk heterojunction (BHJ) morphology of the active layer is essential for optimizing blade-coated organic solar cells (OSCs). Here, the morphology evolution of a highly efficient ternary polymer:nonfullerene blend PM6:N3:N2200 under different blade coating conditions is probed in real-time by in situ synchrotron X-ray scattering and in situ ultraviolet-visible (UV-vis) spectroscopy. Besides, the morphology of blade-coated blend films at different conditions is detailed by ex situ X-ray scattering and microscopic imaging. The ternary blend film exhibited optimized morphology, such as superior molecular stacking structure and appropriate phase separation structure, and boosted photovoltaic performance of the binary blend, as adding a second polymer component to the host polymer:nonfullerene system can balance nucleation and crystallization of polymers and small molecules, facilitating molecular rearrangement to perfect crystallization. Both binary and ternary blends obtained optimized morphology and photovoltaic properties at medium coating speed, mainly attributed to the movement of the polymer and small molecules at the long crystallization and aggregation stage. These findings help understand morphology formation under film drying and provide guidance for optimizing the morphology in blade-coated OSCs. 相似文献
20.
Correlated Donor/Acceptor Crystal Orientation Controls Photocurrent Generation in All‐Polymer Solar Cells 下载免费PDF全文
Marcel Schubert Brian A. Collins Hannah Mangold Ian A. Howard Wolfram Schindler Koen Vandewal Steffen Roland Jan Behrends Felix Kraffert Robert Steyrleuthner Zhihua Chen Konstantinos Fostiropoulos Robert Bittl Alberto Salleo Antonio Facchetti Frédéric Laquai Harald W. Ade Dieter Neher 《Advanced functional materials》2014,24(26):4068-4081
New polymers with high electron mobilities have spurred research in organic solar cells using polymeric rather than fullerene acceptors due to their potential of increased diversity, stability, and scalability. However, all‐polymer solar cells have struggled to keep up with the steadily increasing power conversion efficiency of polymer:fullerene cells. The lack of knowledge about the dominant recombination process as well as the missing concluding picture on the role of the semi‐crystalline microstructure of conjugated polymers in the free charge carrier generation process impede a systematic optimization of all‐polymer solar cells. These issues are examined by combining structural and photo‐physical characterization on a series of poly(3‐hexylthiophene) (donor) and P(NDI2OD‐T2) (acceptor) blend devices. These experiments reveal that geminate recombination is the major loss channel for photo‐excited charge carriers. Advanced X‐ray and electron‐based studies reveal the effect of chloronaphthalene co‐solvent in reducing domain size, altering domain purity, and reorienting the acceptor polymer crystals to be coincident with those of the donor. This reorientation correlates well with the increased photocurrent from these devices. Thus, efficient split‐up of geminate pairs at polymer/polymer interfaces may necessitate correlated donor/acceptor crystal orientation, which represents an additional requirement compared to the isotropic fullerene acceptors. 相似文献